98 Suburban 2WD/5.7L AC Issue - HELP

[shultzee13]

Started off with less than 6 month old AC Delco compressor stopped engaging going down the road on Saturday. Of course now won't blow cold.

In testing the situation I jumped the rear compressor switch connector on the back the compressor to the battery and great news - the compressor engaged.

But now....my AC controller on the dash has no lights when I push activate the AC or Recirculate button and those buttons do nothing.
Plus I have lost control over where the air goes to.
I made a bad situation even worse.

AC relay is brand new. AC fuses in the door panel and under the hood all good.

Did I blow the controller?
Is there a fuse somewhere that works the AC controller?

Hot in Texas so I asking for help here.
Thanks in advance.

[sntrym95]

Does the blower motor still work? If so, then you have power to the switch panel. If nothing that the control panel controls works, then you have a power source issue, like a fuse or wiring issue.

Here is a link to schematics from a factory service manual for a 95, but they should be the same for a 98. https://flic.kr/s/aHsm77966y

[shultzee13]

Originally Posted by sntrym95

Does the blower motor still work? If so, then you have power to the switch panel. If nothing that the control panel controls works, then you have a power source issue, like a fuse or wiring issue.

Here is a link to schematics from a factory service manual for a 95, but they should be the same for a 98. https://flic.kr/s/aHsm77966y

Yes sir the blower motor still works
Posted via Mobile Device

[shultzee13]

Hey Mike
I can't find it on the schematic at all.

Does anyone else know what fuse provides power to the AC controller functions?

Thanks

[sntrym95]

There should be a 25A fuse in the block in the dash by the driver's side door.

[sntrym95]

Also, if the fuse under the hood (50A) is not working then I believe the A/C functions do not work.

[shultzee13]

I do know the 25 amp fuse in the door is good. The one small one labeled AC under the hood is good as well.

I will check the 50 amp fuse and report back.

[shultzee13]

ALL 50 amp fuses are GOOD

[sntrym95]

Ok, I'm still searching for another schematic, but in the meantime can you check the low side pressure port? The compressor will not engage if the low side pressure is too low.

[shultzee13]

Low side pressure port on drier is brand new. Just bought and tested it Saturday.
I have no way to test it again without controller functions.

[sntrym95]

According to another schematic I found there is a 10A fuse for the low pressure switch.

[sntrym95]

I know you said the AC relay is brand new. It seems like it's the only common piece between the controller and the a/c system. can you test that as well just in case?

[shultzee13]

No but since it is brand new I can take that sucker back and get a brand new one.

I wonder what the relay has to do with the controller functions.

[95 S_Trucker]

The 10A fuse is in the underhood fuse box.

There is also a relay in the underhood fuse box.



When testing the A/C system, its never a good idea to use jumpers to get the compressor to work. It's better to check for voltage at connectors than it is to apply voltage to components. There are 2 pressure switches, and the PCM is also involved in the compressor clutch activation. You are probably low on refrigerant. It would be a better case scenario if your HVAC controls are fried. That would be better than having a fried driver in the PCM.


There is no need to start 2 threads for the same problem.

[shultzee13]

I have two separate issues so two different threads. If it takes 10 threads to get AC in Texas and faster help so be it.

[shultzee13]

I am not low on Freon. Levels are accurate with professional set of gauges. I tested the connector with methods that dozens of guys on here have recommended. Not one out of ten said to not do it.

[shultzee13]

Humor me...say someone was low on Freon would that make the controller AC and recirc lights not work when you push them or where to send air?

[sntrym95]

Originally Posted by shultzee13

Humor me...say someone was low on Freon would that make the controller AC and recirc lights not work when you push them or where to send air?

The air deflector should work regardless of the A/C condition, so you should be able to select front vents, defrost, or floor. The A/C light still should come on when low on freon (ask me how I know), but the compressor will not kick on. If the relay is bad, the A/C lights won't come on (to the best of my knowledge).

[95 S_Trucker]

The forum rules dictate the number of threads you should make, not the weather in texas. Your other thread will most likely get deleted or merged with this one. If it gets merged then the posts get funky and out of order.

The only way to know for sure if you have the correct amount of refrigerant is to evacuate and recharge with the correct amount, or to have a functioning system and watch the pressures, and slowly add to the low side until you get good numbers.

You can't tell the proper level by hooking up gauges to a non operating system.

[shultzee13]

If you don't like my post in more than one place then have it deleted. You pointing it out has no relevance over me needing immediate help.
I appreciate your comments but seriously I don't need technicalities right now...I am trying to get to the bottom of this.

It is NOT low on Freon

[95 S_Trucker]

I am not trying to start a pissing match. This forum is a great place because of the knowledgeable people willing to help each other out.

When you joined the forum, you checked a little box that’s says you read and understand the rules.

You should read them all, but specifically read the first 2 sentences and read number 13.

http://67-72chevytrucks.com/vboard/a...t.php?f=34&a=9

If you are in that much of a hurry to get it fixed, go spend hundreds at a shop instead of asking for free advice. We are just sharing our knowledge to help you with your problem.

[shultzee13]

I replaced the controller and now I am back to the original problem of the compressor not engaging.
The very first original problem was the ac stopped blowing cold at idle.
The compressor low side is WAY HIGH in the readings.
The compressor is not locked up and will turn by hand.
Last Saturday just going down the road the compressor stopped engaging.
Blowing hot.
I’m back to my original issue and the symptoms except now Compressor not engaging with low pressure terribly high.

I’ve read that the condenser can cause the issue of not cooling at idle. Any thoughts?
I hate pulling the condenser and going through all that if that’s not it.
Do these symptoms sound like the condenser?

Thank you

[shultzee13]

I replaced the controller and now I am back to the original problem of the compressor not engaging.
The very first original problem was the ac stopped blowing cold at idle.
The compressor low side is WAY HIGH in the readings.
The compressor is not locked up and will turn by hand.
Last Saturday just going down the road the compressor stopped engaging.
Blowing hot.
I’m back to my original issue and the symptoms except now Compressor not engaging with low pressure terribly high.

I’ve read that the condenser can cause the issue of not cooling at idle. I was wondering about that.
I just hate taking out the condenser if this is not the problem.
Thanks to all for the help.

[shultzee13]

Sorry for some reason it loaded response twice from iPad.

[Cabnchassis]

Every GMT400 I've owned, after they went to the center mounted heater, has had electrical issues at the switch panel. The high speed heater switch has been melted at the harness connector, in almost every single one I've ever pulled out. I've pulled 20-25 at wrecking yards, all but 2 showed damage, neither worked in the 3rd or 4th position lol.

Traded a 95 k1500 burb for a 98 Grand Prix GTP, blew the trans then traded it for a 91 k2500 burb with a 6" lift....which is now a 91 Honda CR500 but I digress....The heater panel actually started smoking on the highway, ruined the controls, would have caught fire without attention. Most of them aren't a fire hazard, just don't work on the higher speeds, but it's startling how many of these trucks have visible damage around the high speed switch.

Not sure if its related to the switch based on what you've done, but one time I pulled a heater fuse in summer to fix the control panel in my 91 R3500. Took two weeks to figure out why the transmission was stuck in limp mode. Someone at GM didn't see any problem with powering the DRAC or whatever that thing is off a fuse that you might pull for a hundred reasons, and still need to drive down the road.